1. Field Of The Invention
The present invention relates to the preparation of rigid cellular foam compositions characterized by carbodiimide, isocyanurate and urethane linkages. More particularly, the invention relates to the preparation of foam compositions by the reaction of an organic polyisocyanate with certain oxyalkylated Mannich polyols employing an NCO/OH equivalent ratio of from about 2:1 to 10:1.
2. Prior Art
The preparation of foams containing carbodiimide linkages is well known in the art. Generally, the foams are prepared by condensing an organic polyisocyanate with a catalyst which promotes carbodiimide linkages, optionally in the presence of a blowing agent. Representative of such teachings are the disclosures found in U.S. Pats. Nos. 2.941,966 and 3,645,923. The prior art also teaches that foams containing both carbodiimide and isocyanurate linkages can be prepared by condensing an organic polyisocyanate with a catalyst which promotes both carbodiimide and isocyanurate linkages or with a co-catalyst system, one catalyst promoting carbodiimide linkages and one catalyst promoting isocyanurate linkages. Representative of such teachings are the disclosures found in U.S. Pat. Nos. 3,645,923; 3,657,161; 3,717,596; 3,723,366, and 3,746,709.